The present invention is directed to bicycle transmissions and, more particularly, to an apparatus for assisting a change speed operation in the bicycle transmission.
Various devices have been developed to help reduce the effort needed to operate bicycle transmissions such as derailleurs and internal hub transmissions. Examples of such devices particularly suited to assist the operation of derailleur transmissions are shown in U.S. Pat. No. 5,358,451. The devices shown therein for assisting the operation of a rear derailleur employ multiple moving parts that are in constant motion, thus increasing the amount of moving mass as well as the possibility of premature wear on the components. Devices shown therein for assisting the operation of a front derailleur accommodate only two front sprockets. However, many bicycles have more than two front sprockets. Thus, there is a desire for an assist device that can be used with more than two sprockets. It would also be helpful if the number of continuously moving parts is minimized.
The present invention is directed to an apparatus for assisting a speed change operation in a bicycle transmission. Like prior art devices, the apparatus can accommodate two front sprockets, but the apparatus also can accommodate more than two front sprockets. While it is not critical to realize the full contribution to the art by the present invention, the disclosed embodiments also minimize the number of constantly moving parts, thus reducing inertial forces and wear on the components.
In one embodiment of the present invention, not to be limited thereto, an assisting apparatus for using power from a rotating member to assist the operation of a bicycle transmission comprises a mounting unit and an input transmission member coupled to the mounting unit, wherein the input transmission member moves to at least a first input position, a second input position and a third input position. An output transmission member is coupled to the mounting unit, wherein the output transmission member moves to at least a first output position, a second output position, and a third output position corresponding to the first input position, the second input position and the third input position of the input transmission member, respectively. A rotating member engaging member moves between a rotating member engaging position and a rotating member disengaging position, and a motion transmitting mechanism is provided for transmitting motion from the rotating member engaging member to the output transmission member. A switching mechanism is provided for moving the rotating member engaging member to the rotating member engaging position when the input transmission member is in one of the first input position, second input position or third input position and the output transmission member is not in the corresponding first output position, second output position, or third output position, and for moving the rotating member engaging member to the rotating member disengaging position when the input transmission member is in one of the first input position, second input position or third input position and the output transmission member is in the corresponding first output position, second output position, or third output position.
In another embodiment of the present invention, an assisting apparatus for using power from a rotating member to assist the operation of a bicycle transmission includes many of the elements noted above, but it may or may not accommodate more than two gears. In this embodiment, the input transmission member and the output transmission member are coupled to the mounting member for rotation around a rotational axis. The rotational axis may be common to the input transmission member and to the output transmission member (although such is not necessary), which makes it convenient to detect when the two members are not in the proper corresponding positions.
In another embodiment of the present invention, an assisting apparatus for using power from a rotating member to assist the operation of a bicycle transmission includes many of the elements noted above for the first embodiment, and, like the embodiment noted above, it may or may not accommodate more than two gears. In this embodiment, the switching mechanism includes an axially sliding member that moves in the direction of the rotational axis when the input transmission member moves to one of the first input position or second input position and the output transmission member does not move to the corresponding first output position or second output position. Among other things, this feature allows the switching function to be laterally distributed.
In another embodiment of the present invention, an assisting apparatus for using power from a rotating member to assist the operation of a bicycle transmission includes many of the elements noted above, and it may or may not accommodate more than two gears. In this embodiment, the switching mechanism includes a cam that moves together with the input transmission member and a cam follower that moves with the output transmission member. Among other things, this feature allows direct control of the switching function by the input transmission member and uses fewer components.